FIG. 1 shows the configuration of a conventional mobile communication network. In FIG. 1, one Mobile Switch Center (MSC) may be connected to several Base Station Controllers (BSCs) or Radio Network Controllers (RNCs), but one BSC/RNC can be connected to only one MSC. Such a one-to-many relationship between MSC and BSC/RNC limits the networking scheme to some extent. For example, when MSC1 carries the load of local subscribers only, MSC1 may be designed to have a small capacity during the network plan phase. However, considering a case in which many subscribers registered in MSC2 might flock into the service area of MSC1 in a certain time period, MSC1 should be designed to have a large capacity. Thus, it can be seen that the networking scheme of conventional mobile communication networks is not flexible enough and the network plan is complicated, which tends to cause an increase in the investment costs of the network devices.
To address the above problem, a networking scheme for implementing an MSC pool is proposed in the 3GPP 23.236 protocol. FIG. 2 shows the configuration of a mobile communication network based on an MSC pool. In FIG. 2, one MSC may be connected to several BSCs/RNCs, and one BSC/RNC may be connected to several MSCs too, in which the MSCs constitute an MSC pool with respect to the BSC/RNC. In this network configuration, the load of a BSC/RNC may be shared among several MSCs in the MSC pool. Thus, problems caused by the configuration of the conventional mobile communication networks, for example, complicated network plan and increase in the investment costs of the network devices, may be avoided. For instance, when many subscribers registered in MSC2 swarm into the service area of MSC1, MSC2 may still carry the traffic of these subscribers and MSC1 may only carry the load of the local subscribers because the BSCs/RNCs within the service area of MSC1 are connected to MSC2 too. Therefore, there is no need to design a large capacity for MSC1.
Alternatively, an MSC in the MSC pool may employ a structure in which the carrying function and the controlling function are separated, that is, the MSC may be divided into two parts: an MSC server and a media gateway (MGW). Here, the BSCs/RNCs may implement a full interconnection with the MSC servers in the MSC pool via a full interconnection with the MGWs, as shown in FIG. 3, or implement a full interconnection with the MSC servers in the MSC pool directly without the MGWs. Furthermore, a full interconnection between the BSCs/RNCs and the MSC servers in the MSC pool may be implemented through a full interconnection between the MGWs and the MSC servers in the MSC pool, as shown in FIG. 4.
In the existing networking scheme for an MSC pool, each MSC in the MSC pool has a different signaling point, and thus, a BSC/RNC has to support connection with multiple signaling points so as to identify different MSCs. In traffic processing, a BSC/RNC selects a serving MSC for a mobile station (MS) according to the subscriber ID/Intra-Domain NAS node selection (IDNNS) parameter. For example, upon receipt of a layer 3 service request/initial direct transfer message from the MS, the BSC/RNC parses the subscriber ID/IDNNS parameter information in the layer 3 service request/initial direct transfer message, and allocates the traffic load of the subscribers among the MSC servers in the MSC pool according to the subscriber ID/IDNNS parameter.
It can be seen that in the existing 3GPP 23.236 protocol, a BSC/RNC has to support the MSC pool function provided in the protocol, establish a signaling connection with each different signaling point (i.e. MSC) and implement distribution of the subscriber traffic load, so as to implement the network scheme of the MSC pool. However, BSC/RNCs in the current networks do not support such a function now. In other words, all BSC/RNCs in the current networks have to be upgraded if the networking scheme for the MSC pool is to be supported. Considering the fact that there are a large number of BSC/RNCs in the current networks and different manufacturers have inconsistent plans for the BSC/RNCs to support the MSC pool, it would be very difficult to upgrade the BSC/RNCs in the current networks and the upgrading cost is very high, and the upgrading will influence the services of the current networks greatly.